Reference Values for PCT in Lower Respiratory Tract Infections (LRTI) Patients

Procalcitonin (PCT) Reference ranges/ Interpretation of results

The absolute level of PCT concentrations increase with increasing severity of disease. However, as an expression of individually different immune responses and different clinical situations, the same focus of infection may be associated with varying individual elevations in PCT concentrations.

The optimal cut-off values ranges of PCT are variable and dependent on:

  • The clinical setting (eg, emergency room, ICU, post-operative or trauma patients)
  • The site and extent of the infection (eg, RTI, meningitis, abdominal infection)
  • Co-morbidities (eg, immunosuppression)
  • The clinical implications drawn (eg diagnosis, prognosis, antibiotic stewardship)

Therefore, clinicians should use the PCT results in conjunction with other laboratory findings and clinical signs of the patient and interpret the concrete values in the context with the clinical situation of the patient. The reference ranges below are therefore given for orientational purpose only.

PCT reference ranges for differential diagnosis of Lower Respiratory Tract Infections

  • PCT <0.1 μg/L
    Indicates absence of bacterial infection*:
    Use of antibiotics strongly discouraged, also in the presence of impaired pulmonary reserve in AECOPD
  • PCT ≥0.1 – <0.25 μg/L
    Bacterial infection unlikely:
    The use of antibiotics is discouraged
  • PCT ≥0.25 – <0.5 μg/L
    Bacterial infection possible:
    Advice to initiate antimicrobial therapy
  • PCT ≥0.5 μg/L
    Suggestive of the presence of bacterial infection:
    Antibiotic treatment strongly recommended

* Low PCT levels do not automatically exclude the presence of bacterial infection. Such low levels may be obtained, e.g., during the early course of infections, in localized infections and in subacute endocarditis. Therefore, follow-up and re-evaluation of PCT in clinical suspicion of infection is pivotal. The PCT measuring technique should be chosen dependent on intended clinical use.

CAVE: For use of PCT for differential diagnosis of lower respiratory tract infections (LRTI) only sensitive PCT assays can be used which can precisely detect PCT concentrations of 0.1 ng/ml.


Sensitive B·R·A·H·M·S PCT (Procalcitonin) assays

Sensitive B·R·A·H·M·S PCT assays available:


Reference Values for PCT in Sepsis Patients

SIRS, Sepsis, Severe Sepsis, and Septic Shock are categorized according to the criteria of the consensus conference of the American College of Chest Physicians/Society of Critical Care Medicine.

Reference Values for PCT in Sepsis >

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